Obama administration officials are declining to provide specific details about an unprecedented upcoming purchase of Iranian nuclear materials, an $8.6 million exchange that is likely to be funded using American taxpayer dollars, according to conversations with multiple administration officials and sources in Congress.

The administration is preparing to purchase from Iran 32 tons of heavy water, a key nuclear material, in a bid to keep Iran in compliance with last summer’s comprehensive nuclear agreement.

But administration officials have declined to provide specific details to Congress and reporters about how exactly it will pay for the purchase, as well as other information, until the deal has been completed.

The effort to withhold key information about the purchase, which is likely to be paid in some form using U.S. taxpayer dollars, is causing frustration on Capitol Hill, according to multiple sources who disclosed to the Washington Free Beaconthat the administration is rebuffing congressional attempts to discern further information about the deal.

Experts further disclosed to the Free Beacon that the exchange is likely to legitimize Iran’s research into plutonium, knowledge that would provide the Islamic Republic with a secondary pathway to a nuclear weapon capability.

Officials from both the Treasury and Energy departments told the Free Beacon that details about the payment are being withheld until the purchase is complete. Iran is expected to deliver the heavy water to the United States in the “coming weeks,” officials confirmed.

“We cannot discuss details of the payment until after the purchase is complete,” a Treasury Department official who was not authorized to speak on record told the Free Beacon. “The Department of Energy’s Isotope Program plans to pay Iran approximately $8.6 million dollars for 32 metric tons of heavy water.”